I just got an email from Virgin Money and wonder if the same applies to Starling? I would assume so, though I don’t remember reading anything from them about this.
Mastercard® has altered the way it handles foreign transactions when you spend money abroad. From 11 August, your purchases and cash advances will normally be converted to pounds sterling on the same day. This means you don’t need to worry about a change to the exchange rate after you spend.
When you bought something in another currency previously, it would be converted using the exchange rate on the day it left your account. This could have been a few days after your purchase.
This would be a great change as I often see a few extra pence leave my account a few days later, which screws up my round-ups!